Recently, downsizing of an acoustic device is progressed, and downsizing and/or reduction of thickness (hereinafter, referred to as “downsizing and the like”) is also progressed for an acoustic speaker device. However, it is known that the reproduction of the bass range is difficult since the acoustic speaker device with the downsizing and the like has smaller volume of the cabinet.
More specifically, a general acoustic speaker device is configured to include a speaker unit incorporated in a cabinet. When electric signal is applied to the speaker unit, air in the cabinet is compressed by vibration of the speaker, which serves as an air spring to disturb the movement of the speaker. Smaller volume of the cabinet exhibits larger influence for preventing the movement of the speaker, and therefore this reduces the sound pressure level particularly in the bass region, increasing the lowest resonance frequency. Consequently, in order to enhance the ability to reproduce the bass range, it is necessary to increase the volume of the cabinet, and nevertheless, the increased volume would disturb the downsizing and the like of the acoustic speaker device.
Thus, regardless of whether the downsizing and the like is achieved, various types of technologies for improving ability to reproduce the bass range are conventionally proposed in the field of the acoustic speaker devices.
For example, an acoustic speaker device, which is configured to have a plurality of acoustic fins mounted on a wall of a cabinet in slant relation and an opening section provided at a terminal end of the acoustic fin, is disclosed in Patent Literature 1. According to this configuration, the acoustic fins form a rectangular three-dimensional spiral sound path to provide increased massive feeling in the bass range.
Also, Patent Literature 2 discloses an amplification equipment assembly, which is configured to have agglomerates of an adsorbing material such as activated carbon and the like (material agglomerates) in a cabinet (box). According to this configuration, activated carbon rapidly adsorbs or eliminates compression or expansion of the gas in the cabinet generated by vibration of the speaker unit (more specifically, diaphragm). This can suppress the pressure fluctuation within the cabinet, so that decrease in the sound quality level in the bass range can be prevented.
Also, Patent Literature 3 discloses an acoustic enclosure employing activated carbon provided in a cabinet, which is at least partially hydrophobic or is treated to be hydrophobic. When the activated carbon adsorbs water vapor, water molecules are adsorbed in pores of the activated carbon to be blocked, disturbing adsorption of air. Thus, Patent Literature 3 employs leastwise partially hydrophobic activated carbon.
Meanwhile, zeolite is known as a typical adsorbing material as well as the activated carbon, and various types of technologies for employing the zeolite by processing thereof to form film-like configuration or is sheet-like configuration are proposed.
For example, Patent Literature 4 proposes a film-like gas adsorption material, which is produced by extruding a synthetic resin containing a zeolite-based adsorbent at 1 to 50% wt. to form a film shape and then stretching the film-shaped resin. Adsorption ability for ammonia and hydrogen sulphide is evaluated in the sections of Examples in Patent Literature 4.
Also, Patent Literature 5 proposes a technology related to a vacuum insulation member employing multilayer films, in which zeolite as a getter material is kneaded in resin films constituting the multilayer films.
The multilayer film is configured to be formed by laminating polyethylene terephthalate (PET) film, aluminum foil and polyethylene (PE) film, and the vacuum insulation member is configured that the periphery of this multilayer film is thermally sealed to provide a bag shape and powder silica and the like as an aggregate is charged in the interior thereof, and the interior is vacuum-evacuated and then the opening section is sealed. Zeolite or a mixture of zeolite and activated carbon are kneaded as a getter member in the PET film and in the PE film. This allows the getter member to adsorb moisture, carbonic acid gas and the like from the outside of the multilayer film before entering into the film.